Complex regional pain syndrome: state of the art update

Effectiveness of Intravenous Immunoglobulin for Management of Neuropathic Pain: A Narrative Review

Administrations of intravenous immunoglobulin (IVIG), an immune-modulating blood-derived product, may be beneficial for managing neuropathic pain. Here, we review previous studies to investigate the effectiveness of IVIG in managing neuropathic pain due to various neurological disorders. The electronic databases PubMed, Scopus, Embase, and the Cochrane Library were searched for studies published up to February 2020. Two reviewers independently assessed the studies using strict inclusion criteria. Ten studies were included and qualitatively analyzed. The review included patients with pain due to complex regional pain syndrome (CRPS), diabetic polyneuropathy, and others, such as postherpetic neuralgia and trigeminal neuralgia. We found that IVIG may be one of the beneficial options for managing neuropathic pain from various neurological disorders. In the four articles reviewed, no major adverse effects were reported, and the trend was toward a positive pain-reducing effect in eight articles. However, to confirm the benefits of IVIG on reducing neuropathic pain, more high-quality studies are required.

Trends in Medicalization of Children with Amplified Musculoskeletal Pain Syndrome

Objective

The objective of this survey was to describe trends over time in medicalization of children with Amplified Musculoskeletal Pain Syndrome (AMPS).

Design

A retrospective evaluation was conducted using self-reported data from patients presenting to the pain clinic between January 1, 2008 and December 31, 2014, who were diagnosed with AMPS.

Setting and Subjects

This was a medical record review of 899 subjects ages 3-20 presenting with Amplified Musculoskeletal Pain Syndrome. Subjects were included if they presented to a single tertiary specialized clinic and obtained a diagnosis of AMPS between January 1, 2008 and December 31, 2014.

Methods

Information collected from subjects' medical records included: past medications, current outpatient medications, procedures, aids, therapies, studies, professionals seen, hospitalizations, and surgeries. Trends in medicalization were analyzed by year of initial visit.

Results

Medication use, procedures, studies, therapies, professionals seen, hospitalizations, and surgeries in children with AMPS all increased significantly by year ( P  < 0.001). The degree of physical dysfunction, pain, and the use of aids did not significantly increase.

Conclusions

Children with amplified musculoskeletal pain syndrome are becoming increasingly medicalized. Increased medicalization introduces risk of iatrogenic injury and burdens families with unnecessary medical costs. The significant increase in medicalization of children with AMPS is not related to an increase in patient reported pain, which is evidenced by the lack of significant increase in patients' pain score, pain duration, or functional disability at the time of their initial evaluation.

Children and adolescents with complex regional pain syndrome: more psychologically distressed than other children in pain?

BACKGROUND

Historically, in both adult and pediatric populations, a lack of knowledge regarding complex regional pain syndrome (CRPS) and absence of clear diagnostic criteria have contributed to the view that this is a primarily psychiatric condition.

OBJECTIVE

To test the hypothesis that children with CRPS are more functionally disabled, have more pain and are more psychologically distressed than children with other pain conditions.

METHODS

A total of 101 children evaluated in a tertiary care pediatric pain clinic who met the International Association for the Study of Pain consensus diagnostic criteria for CRPS participated in the present retrospective study. Comparison groups included 103 children with abdominal pain, 291 with headache and 119 with back pain. Children and parents completed self-report questionnaires assessing disability, somatization, pain coping, depression, anxiety and school attendance.

RESULTS

Children with CRPS reported higher pain intensity and more recent onset of pain at the initial tertiary pain clinic evaluation compared with children with other chronic pain conditions. They reported greater functional disability and more somatic symptoms than children with headaches or back pain. Scores on measures of depression and anxiety were within normal limits and similar to those of children in other pain diagnostic groups.

CONCLUSIONS

As a group, clinic-referred children with CRPS may be more functionally impaired and experience more somatic symptoms compared with children with other pain conditions. However, overall psychological functioning as assessed by self-report appears to be similar to that of children with other chronic pain diagnoses. Comprehensive assessment using a biopsychosocial framework is essential to understanding and appropriately treating children with symptoms of CRPS.

Synaptic conversion of chloride-dependent synapses in spinal nociceptive circuits: roles in neuropathic pain

Electrophysiological conversion of chloride-dependent synapses from inhibitory to excitatory function, as a result of aberrant neuronal chloride homeostasis, is a known mechanism for the genesis of neuropathic pain. This paper examines theoretically how this type of synaptic conversion can disrupt circuit logic in spinal nociceptive circuits. First, a mathematical scaling factor is developed to represent local aberration in chloride electrochemical driving potential. Using this mathematical scaling factor, electrophysiological symbols are developed to represent the magnitude of synaptic conversion within nociceptive circuits. When inserted into a nociceptive circuit diagram, these symbols assist in understanding the generation of neuropathic pain associated with the collapse of transmembrane chloride gradients. A more generalized scaling factor is also derived to represent the interplay of chloride and bicarbonate driving potentials on the function of GABAergic and glycinergic synapses. These mathematical and symbolic representations of synaptic conversion help illustrate the critical role that anion driving potentials play in the transduction of pain. Using these representations, we discuss ramifications of glial-mediated synaptic conversion in the genesis, and treatment, of neuropathic pain.